Current differential protection method during TA
Technical field
The present invention relates to electricity field, relate in particular to the saturation process of in the high-voltage fence relaying protection, discerning TA (current transformer), also relate to a kind of TA current differential protection method when saturated simultaneously.
Background technology
In high-voltage fence, the electric current of carrying on the high-tension line is generally hundreds of amperes to thousands of amperes, and the little electric current of secondary that so big electric current needs to be converted to 1A specification or 5A specification through TA (current transformer) is introduced protective relaying device.Under the normal condition, the secondary output current of TA can truly reflect the primary current of circuit, but under failure condition, reach the effect of DC component in the fault current greatly owing to fault current, iron core is very fast saturated, so primary current all becomes exciting current, secondary current is almost nil, and it is saturated that this phenomenon is called TA.When TA was saturated, the secondary output current of TA no longer truly reflected the circuit primary current.
The reliability of high voltage power transmisson system protective relaying device is the assurance of power system safety and stability operation.When the protected circuit external area error, possible owing to short circuit current causes TA saturated greatly, thus the progress of disease is distorted to the current waveform of secondary side.Because the difference in the TA transient response of both sides may obtain bigger difference stream at secondary side.Comparatively common a kind of situation is that the appearance of both sides TA one side is saturated, and a side is unsaturated, and this time difference stream will reach a higher value.Be to guarantee reliability, protection is at present mostly adopted: 1. detect TA and raise threshold and improve ratio brake coefficient K value increase braking action after saturated; 2. latch-up protection in short-term prevents to protect malfunction.
The existing saturated detection method of TA is generally distorted waveform feature detection method, in two cycles after big electric current occurring, a sampled point appears, and its difference between current score value is less than 2.5A (5ACT) or 0.5A (1ACT), and this point sampling value is less than 2A (5ACT) or 0.4A (1ACT), and satisfies
And
Or 0.3A (1ACT), wherein i
0Be the difference value of current sampling point and last sampled point,
Be any difference value before sampled point before the half cycle and its; There is current peak to occur greater than 11.6A (5ACT) or 2.3A (1ACT);
Above-mentioned wave distortion feature detection method, the major defect of existence is that detection time is slow, needs at least two cycles, can greatly reduce the responsiveness of protection like this, the overall performance of influence protection.
At present technology detect TA saturated after, the K value is brought up to 0.9, yet causes that TA is saturated when serious when external area error, malfunction is still within the bounds of possibility.
Summary of the invention
At the deficiencies in the prior art, purpose of the present invention proposes the saturated recognition methods of a kind of effective TA.
Simultaneously, the current differential protection method when the present invention also aims to provide a kind of TA saturated can export fast so that protect when internal fault, and external fault causes when TA is saturated can effectively prevent malfunction.
For achieving the above object, technical program of the present invention lies in adopting the saturated recognition methods of a kind of TA, it is saturated that this invention adopts the differentiation of segmentation integral of pulse shape method whether TA to take place.
Described segmentation integral of pulse shape method is the spacer that current waveform is divided into 5ms, and every section current waveform is carried out area integral, differentiates the difference of several integral areas then, if the integral area of several sections waveforms is basic identical, judges that TA does not take place saturated; If the integral area of several sections waveforms differs bigger, it is saturated to judge that TA takes place.
Maximum area in detecting each section area and minimum area differ thinks when being 1.3 times that the TA wave distortion is serious, and it is saturated to judge that TA takes place, and enters the saturated processing logic of TA.
Simultaneously, the current differential protection method when TA is saturated that the present invention adopts, whether adopt segmentation integral of pulse shape method to differentiate TA saturated, and this method comprises the steps:
A. the short window that makes full use of TA linear transform time delay exports method fast;
B. just drop into the saturated discriminating processing of TA during the short distance transmission line;
C. just drop into the saturated discriminating processing of TA during a half breaker wiring system;
D. protection detects the size of two ends electric current in good time, only drops into the saturated discriminating processing of TA when the two ends electric current is simultaneously out-of-limit;
E. improving the K value prevents greater than 1 that external area error TA is saturated and causes malfunction.
Utilize the troubles inside the sample space of linear progress of disease time of unsaturation and the short window data of 4ms~5ms to export fast.
The realization that protection drops into the saturated discrimination function of TA adaptively is unlikely to protect overall performance to be affected.
Device recognize TA saturated after, improve the K value greater than 1, representative value K gets 1.2.
Maximum area and the minimum area of the present invention in detecting each section area differs and thinks when being 1.3 times that the TA wave distortion is serious, enters the saturated processing logic of TA.This method detects cycle of the saturated need consuming time of TA, and outstanding feature is effectively simple.Do not influence the protection responsiveness in the saturated processing method of TA can guarantee to distinguish during catastrophe failure, external area error causes and effectively prevents malfunction when TA is saturated.The saturated processing method of TA is a self adaptation input method, and is little to the influence of protection overall performance.
Description of drawings
Fig. 1 is the typical waveform of TA electric current when saturated;
Fig. 2 is that a half breaker system external area error causes the saturated schematic diagram of TA;
Fig. 3 is for differentiating the saturated segmentation integral of pulse shape method of TA;
Fig. 4 is the influence of ratio brake coefficient K value to the differential protection active region.
Embodiment
Following mask body is narrated detailed content of the present invention:
One, the short window of the troubles inside the sample space realization of outlet fast
When TA is saturated; because TA has the saturated one preceding linear transform period (3~5ms); the fault component phase-splitting difference element of protection makes full use of the short window Data Detection fault of unsaturated linear transform period of this section and 4ms~5ms; can export rapidly if detect troubles inside the sample space, thereby avoid the saturated influence of TA protection.It should be noted that owing to contain bigger harmonic component in the short window data of fault initial stage, is again some outlet fast, so should suitably increase the action threshold of fault component phase-splitting difference element and improve the K value.
Two, the realization of the saturated real-time input of TA
The saturated analysis that a situation arises of TA can be found by to the transmission line external area error time:
The short distance transmission line because line impedance is little, may cause that when external area error TA is saturated when large power supply.After transmission line length surpassed 10km, line impedance increased, and external area error causes that the saturated possibility of TA is very little, and therefore, this invention only just drops into the saturated differentiation logic of TA when short-term road.The identification of short-term road is realized according to user's definite value automatically by protective device.
It is saturated TA also to take place easily during fault outside the half breaker system time zone, and this is that therefore, this invention also drops into the saturated differentiation logic of TA when a half breaker system owing to the reason (see figure 2) of multichannel fault current stack.The identification of a half breaker system is also realized according to user's definite value automatically by protective device.
In view of short-term road and half breaker system cause that not necessarily TA is saturated when the external area error, this invents the size of real-time detection line two ends electric current, only at the two ends electric current simultaneously greater than may cause the saturated threshold of TA (1.5In) time, just drop into the saturated differentiation logic of TA.So processing method is reduced to minimum to the entire effect of protection the differentiation of TA saturation detection.
Three, the saturated recognition methods of TA
It is saturated that this invention adopts the differentiation of segmentation integral of pulse shape method whether TA to take place, this method is actually the spacer (see figure 3) that current waveform is divided into 5ms, every section current waveform is carried out area integral, differentiate the difference of several integral areas then, when wave distortion does not take place in TA because sine-shaped symmetry, the integral area of several sections waveforms is basic identical, and when wave distortion took place TA, the integral area of several sections waveforms differed bigger.The degree of TA wave distortion not simultaneously, it is also different that the integral area of several sections waveforms differs size, maximum area and the minimum area of the present invention in detecting each section area differs and thinks when being 1.3 times that the TA wave distortion is serious, enters the saturated processing logic of TA.This method detects cycle of the saturated need consuming time of TA, and outstanding feature is effectively simple.
Four. improve the analysis of K value
K even the both sides electric current in the same way, still had the tripping district greater than 1 o'clock as shown in Figure 4.Get K less than 1 during normal the operation, active region is big, and is highly sensitive, but under the short-term road situation, the outer big current failure in district causes just possibility malfunction when TA is saturated.Therefore device recognize TA saturated after, K value gets 1.2, dwindles active region, prevents that the outer current failure greatly in district from causing generation malfunction when TA is saturated.Judge TA when saturated when device, it is differential to withdraw from zero-sequence current when improving differential current element K value.